Electromagnetic interference shielding device

ABSTRACT

A shielding device consists of a contact spring (1) having a triangular profile which is open at one triangular point. With the free legs (2, 3) the contact spring (1) is slipped over the edge of a housing member (10), such as a door, side wall, or the like. Following the closure or the assembly, one of the legs (2,3) is applied to the other housing member (12) forming a gap with the first member (10), which gap is to be conductively bridged.

BACKGROUND OF THE INVENTION

The invention relates to an electromagnetic interference shieldingdevice in the form of a contract spring element for closing a gap orclearance between housing or covering-panel members of a cabinet or rackcontaining electronic equipment.

From German Pat. No. 2,039,681 there is known one such shielding device,which consists of spring contact elements freely cut out of a sheetmetal strip having an L-shaped cross section. The shielding device iscapable of being inserted into the grooves of housing members. Onehousing member, e.g. a corner profile, comprises specially shapedgrooves in which the contact spring strips as well as the respectiveneighbouring housing members (closing plates) are slipped. With the aidof the contact spring strips, the housing members are connected in anelectrically conductive manner and, at the same time, electromagneticinterference shielding for the interior of the housing is provided. Thedisclosed type of shielding device, however, is only suitable for usewith fixed housing members, hence not with doors or similar movingparts.

For the electromagnetic interference shielding of door joints there isdisclosed, for example, in the German Pat. No. 2,522,186, a sealingelement which is disposed in the door. In this construction, behind anangled-off door edge, there is mounted a flexible ledge. Between thisledge and a parallel-extending angle section there is clamped the flapof an electrically conducting sealing strip which is rolled over at itsfree end and, in this part, may be filled with an elastic core. Uponclosing the door, the rolled part is compressed and establishes thecontact between the door and the housing.

Another door-joint shielding is known from German OffenlegungsschriftNo. 3,219,263 which, however, is only for use on the hinge side. On thisside, the door panel is bent at least semicircularly, with the roundingbeing covered by a spring plate connected on one hand to the door and,on the other hand, to the door frame.

Finally, from German Offenlegungsschrift No. 3,210,843, there is known acontact device for housing members capable of being moved in relation toone another, in which a knife-shaped extension of one housing membercomes into snap-engagement with a groove lined with contact springs, ofthe other housing member.

SUMMARY OF THE INVENTION

It is the object of the invention to provide an electromagneticinterference shielding device which is easy to manufacture and toassemble, and which can be used for closing gaps or clearances betweenstationary as well as between movable housing members. This device is toensure a good contact-making. On the other hand, when attached to adoor, the closing pressure is not to become excessively high.

This object is achieved by providing a contact spring having a generallytriangular profile that is open at one point. The legs adjacent the openpoint are slipped over an edge of one of the housing members forming agap, and a leg is applied to another housing member forming the gap. Theadvantages of this solution reside in that it not only meets the givenrequirements, but that the contact springs, also without any specialmeasures, are capable of being used on the housing members. That is,they are neither in need of the guiding grooves of special sections, norof additional mounting means. The seating of the contact springs can beimproved with the aid of small flaps engaging into simple openings,which is of particular advantage in the case of moving parts, such asdoors.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a shielding device according to the invention in the shapeof a contact spring, in a perspective representation,

FIG. 2 shows a double contact spring resembling the one of FIG. 1, inperspective representation, and

FIG. 3 is the cross-sectional view of a contact spring placed on to theedge of a door.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The contact springs 1 as shown in FIGS. 1 to 3 have a triangular profilewhich almost corresponds to that of an isosceles triangle. One of thetriangular points is open, that is, where the two nearly equally longlegs 2 and 3 form an acute angle. The leg 2 is bent off inwardly at itsfree end to form a narrow lip 4 extending almost in parallel with theconnecting, short leg 9.

The free ends of the two legs 2 and 3 are each provided in their centerswith a flap 5 or 6, each of which, in turn, is slightly bent toward theinside. While FIG. 1 shows one single contact spring 1, FIG. 2 shows adouble contact spring 1 (as seen from the other side with respect toFIG. 1). The difference merely resides in that two contact springs arejoined by a remaining web 8 on one of the legs. The two can be separatedwith the aid of a transversely extending incision 7 in the profile. Theweb 8 is appropriately within the edge area of the smooth leg 3. In thisway, the contact spring 1 can be manufactured on a production line andthen divided, in accordance with requirements, by cutting the web 8,into single, double or multiple contact springs. The contact spring 1 ismade from a relatively thin spring plate, such as spring steel, springbronze, etc. It is featured by small dimensions, a large springdeflection and a small pressure rise throughout the entire springexcursion. Its contact resistance is low-ohmic.

As is illustrated in FIG. 3, the contact spring 1 is simply slipped onto the edge of the housing member 10 and is self-lockingly retained inposition by the flaps 5 and 6 engaging into the opening 11. In thenormal position, the leg 2 is applied to the housing member 12. Thehousing member indicated by the reference numeral 10 is a door of ahousing or cabinet or of the covering panel of a rack containingelectronic equipment which, when being closed, is swivelled against thehousing member or wall 12 of the housing in the direction as indicatedby the arrow 13. The contact spring 1, in the course of this, deflectstoward the other side as indicated by the arrow 14. By the contactspring 1 there is established a metallic connection in the gaps of thehousing, so that all housing members or parts of the covering panels,such as doors, side walls, etc., are electrically connected among eachother and to the racks, and are thus also grounded. At the same time, itis also easily possible to achieve RF shielding. Considering that thearrangement of the contact springs is variable, the spacings can beeasily adapted to the frequencies in order thus to respectively obtain acomplete shielding of the housing.

What is claimed is:
 1. An electromagnetically shielded housing forelectronic equipment, comprising:first and second housing members with agap between them, the first housing member having an edge and having anopening adjacent the edge; and a contact spring element to close the gapbetween the first and second housing members, the contact spring elementhaving a profile with three legs disposed in a generally triangularconfiguration that is open at one point, the generally triangularconfiguration almost corresponding to the configuration of an isoscelestriangle, two of the legs being adjacent the open point and beingslipped over the edge of the first housing member, one of the legs beingapplied to the second housing member, wherein one of the legs adjacentthe open point has a free end that is bent toward the interior of thetriangle to form a narrow lip having, the lip having an inwardlyangled-off flap, and wherein the other of the legs adjacent the openpoint has a free end with an inwardly angled-off flap, the flapsengaging the opening.
 2. The shielding device in claim 1, wherein thecontact spring element is elongated and has at least one transverselyextending incision which divides the spring element so that only aconnecting web remains in one of the legs adjacent the open point. 3.The shielding device of claim 1, wherein the first and second housingmembers comprise panels that are substantially parallel.
 4. Theshielding device of claim 1, wherein the first housing member has apredetermined thickness, and wherein the leg opposite the open point hasa portion that is substantially straight when the contact spring elementis not subjected to stress, the substantially straight portion of theleg opposite the open point having a length that substantially exceedsthe thickness of the first housing member.
 5. The shielding device ofclaim 6, wherein the contact spring element is pivotable with respect tothe opening.
 6. The shielding device of claim 5, wherein the flapsengage the opening by entering the opening.
 7. An electromagneticallyshielded housing for electronic equipment, comprising:a first housingmember having an edge and having an opening adjacent the edge; a secondhousing member mounted adjacent the first housing member; and a contactspring element having a profile with three legs disposed in a generallytriangular configuration that is open at one point, the triangle beingsubstantially isosceles and the open point being at the apex thereof,wherein two of the legs are adjacent the open point and are slipped overthe edge of the first housing member, wherein one of the legs restsagainst the second housing member, wherein one of the legs adjacent theopen point has a free end that is bent toward the interior of thetriangle to form a narrow lip, the narrow lip having an inwardlyangled-off flap which engages the opening in the first housing member,and wherein the other leg adjacent the open point has an inwardlyangled-off flap which engages the opening in the first housing member.8. The shielded housing of claim 7, wherein the contact spring elementis elongated and has at least one transversely extending incision whichdivides the spring element so that only a connecting web remains in oneof the legs adjacent the open point.
 9. The shielded housing of claim 7,wherein the housing members and the contact spring element areconductive, and wherein the contact spring element electrically connectsthe housing members.
 10. The shielded housing of claim 7, wherein thehousing members have surfaces that are substantially parallel.
 11. Anelectromagnetically shielded housing for electronic equipment,comprising:a first housing member having inner and outer sides andhaving an edge between the inner and outer sides; a second housingmember mounted adjacent the first housing member; and a contact springelement made of sheet metal and having an outer leg with a free end, aninner leg with a free end, and a connecting leg which joins the innerand outer legs so that the free ends thereof are directed towards oneanother, the connecting leg having a length that is substantiallygreater than the distance between the inner and outer sides of the firsthousing member, the contact spring element additionally having mountingmeans disposed on at least one of the free ends for pivotably mountingthe contact spring element on the first housing member, the free end ofthe outer leg being in contact with the outer side of the first housingmember, the free end of the inner leg being in contact with the innerside of the first housing member, the connecting leg being spaced apartfrom the edge of the first housing member, and the inner leg resilientlyengaging the second housing member.
 12. The shielded housing of claim11, wherein the first panel has an opening adjacent the edge, andwherein the mounting means comprises a flap extending from at least oneof the free ends into the opening.
 13. The shielded housing of claim 11,wherein the first panel has an opening adjacent the edge, and whereinthe mounting means comprises a flap extending from the free end of theouter leg into the opening and another flap extending from the free endof the inner leg into the opening.
 14. The shielded housing of claim 13,wherein the inner leg is bent toward the outer leg to provide a narrowlip adjacent the free end.
 15. The shielded housing of claim 11, whereinthe inner leg is bent toward the outer leg to provide a narrow lipadjacent the free end of the inner leg.
 16. The shielded housing ofclaim 15, wherein the first panel has an opening adjacent the edge, andwherein the mounting means comprises a flap extending from the lip intothe opening.
 17. The shielded housing of claim 16, wherein the mountingmeans further comprises another flap extending from the free end of theouter leg into the opening.
 18. The shielded housing of claim 17,wherein the contact spring element is generally configured as anisosceles triangle, having an open apex angle at the free ends of theinner and outer legs.
 19. The shielded housing of claim 11, wherein thefirst and second housing members are panels that are substantiallyparallel.